This application claims priority under 35 U.S.C. 119 of German Patent Application No. 201 02 471.3, filed Feb. 13, 2001.
The invention relates to a thread rolling head, more specifically an axial or radial thread rolling head.
Thread rolling heads are generally known. An axial thread rolling head, for example, is disclosed in DE 44 30 184. Just as other conventional axial thread rolling heads do it has three profiled rolling dies offset by 120xc2x0 from each other which are rotatably supported in a bearing unit. The bearing unit is held by a shank which is gripped in a machine tool. The rolling head is held in place in the sense of rotation, but can move axially. The rolling head is pressed onto the rotating tool with the forward feed being performed by the rolling head, which is freely movable axially, while the thread is being formed. The profiled rolling dies are mounted on eccentric shafts which when actuated bring the rollers into engagement with the tool. The eccentric shafts are operated via pinions which mesh with a central toothed gear or a circular toothed gear with the circular toothed gear when operated cause the profiled rolling dies to be shifted relative to the workpiece. The eccentric shafts are preferably biased by a spiral-coiled spring and will be biased into the initial position at the end of machining. The spiral-coiled spring is supported in a spring housing which constitutes a clutch portion for a claw clutch with these parts having disposed therebetween an actuation ring which interacts with a ring-shaped ball cage retainer. A front-end plate at the front end of the axial thread rolling head serves for supporting the eccentric shafts.
A radial rolling head as is known, for example, from DE 42 36 085 or DE 197 01 049 features profiled rollers or rolling dies which exhibit a course of their surface that helically ascends in opposition to their sense of rotation over the circumference. The rolling dies are coupled to a gearing mechanism and an inter-locking mechanism is automatically disengaged after every complete turn of the rolling dies. The interlocked state is released prior to the rolling operation, i.e. by the workpiece which is to be deformed by the rolling dies. Flattened areas of the rolling dies oppose each other in the initial position to thereby permit the insertion of the workpiece. The rolling dies are rotated via pinions which mesh with a central toothed gear which is driven by an appropriate drive. This purpose is served by a spring mechanism which turns the rolling dies until they get into contact with the workpiece. The rolling operation will start subsequently, and the frictional grip existing between the rotated workpiece and the rolling dies causes the rolling dies to be kept rotating and the spring mechanism to be tensioned again. The rolling operation always lasts only for a single rotation of the rolling dies. The spring mechanism includes a spring housing which is gripped in the machine tool via a shank. Pinions of the drive interact with a toothed rim with the pinions acting on pinions coupled to the shafts of the profiled rollers. The latter ones are supported in a gearing plate.
What ensues from the above explanations is that the axial rolling head is either at stoppage or rotates while the workpiece, in turn, is rotating or is at stoppage. This allows to produce nearly all thread shapes with the profile length not being limited. The radial rolling head permits extremely short lengths of thread runout and makes possible extremely short threads. Moreover, the machining time is very short. Even here, the workpiece is either at stoppage or rotates while the rolling head either is rotating or is at stoppage.
For more details, reference is made to the above mentioned state of the art and the company publication xe2x80x9cFette Rollsystemexe2x80x9d. The rolling systems described are frequently employed in so-called automatic rolling machines which operate at short switching times and high accelerations. It is understood that the rolling heads which are relatively heavy set limits to the switching and machining times.
Therefore, it is the object of the invention to provide an axial and/or radial rolling head that admits shorter switching times and higher accelerations.
The axial thread rolling head of the present invention has formed therein at least the bearing unit and/or the spring housing in titanium or a titanium alloy. According to an aspect of the invention, an actuation ring between the clutch portion and the spring housing and/or a front-end plate for supporting the eccentric shafts are also formed in titanium or a titanium alloy. According to another aspect of the invention, a toothed rim for the pinions seated on the eccentric shafts is also formed in titanium or a titanium alloy.
The radial thread rolling head according to the invention has formed therein the shank and/or the spring housing and/or the gearing plate in titanium or a titanium alloy. According to an aspect of the invention, a front-end plate supporting the rolling dies is also formed in titanium or a titanium alloy.
The inventive thread rolling heads have formed therein those components which have a relatively large mass, but are not subjected to particular stresses, in the relatively light-weight titanium or a titanium alloy. This way makes it possible to significantly reduce the weight of the thread rolling heads, namely by from 25 to 30%.
The present invention includes an axial thread rolling head comprising a bearing unit including the rolling dies in which the rolling dies are rotatably supported via eccentric shafts, a shank which is axially movable with respect to the bearing unit and has a clutch portion which, in a first axial relative position, interacts with a claw clutch portion of a ring-shaped spring housing of the bearing unit that is rotatably supported on the shank, which couples the two components in a torsion-resistant manner, a first gearing between the shank and the eccentric shafts for varying the mutual spacing of the rolling dies, a spiral-coiled spring between the shank and the bearing unit such that rotating the bearing unit with respect to the shank in a first sense of rotation will cause the spiral-coiled spring to tension the shank and the bearing unit towards each other into the first relative position and that, in a second axial relative position in which the claw clutch portions are out of engagement, the tensioned spiral-coiled spring will rotate the bearing unit relative to the shank into a second sense of rotation, which will open the rolling die via the first gearing, and mechanical switching means which if in a contact with a workpiece will move the shank and the bearing unit into the second relative position, which involves that at least the bearing unit and the spring housing are formed from titanium or a titanium alloy.